1. Field of the Invention
The present invention relates to the production of novel phosphosilicate glass (PSG) dielectric compositions having improved gap-fill properties and a low dielectric constant, whereby via holes and interlevel dielectric layers can be completely deposited in a single continuous operation to the exclusion of voids, and the deposited PSG has a low dielectric constant and sodium-barrier properties.
2. State of the Art
A wide variety of glass compositions, including phosphosilicate glass compositions are known as gap-fill and interlevel dielectric compositions. Generally such gap-fill compositions are deposited in multiple deposition/multiple etch steps in order to fill the gaps or vias incrementally and prevent the trapping of gases which can produce voids in the deposit. Such procedure is time-consuming, expensive and reduces efficiency.
It is known that several modified dielectric glass compositions have better gap-fill properties than conventional silica glass compositions, including boron-containing phosphosilicate glass, and phosphorous-doped spin-on glasses. However, there is a need for a gap-fill glass composition having better gap-filling properties and having a lower dielectric constant than compositions currently available.
It is also known that the presence of fluorine-containing gas enhances the filling of gaps or voids with dielectric glass compositions by etching the top of the via holes or gaps during the filling operation. However, conventional phosphosilicate glass compositions are relatively unstable and unsatisfactory for use as gap-filling dielectric glass compositions.
Reference is made to U.S. Pat. No. 4,535,528 which discloses a process for enhancing the reflow properties of phosphosilicate glass by the implantation of arsenic ions.
Reference is made to U.S. Pat. No. 5,275,977 which discloses a CVD process for depositing and simultaneously etching a silicon oxide dielectric layer from a film-forming plasma containing a fluorine gas.
Reference is made to U.S. Pat. No. 5,215,787 which discloses a process for the chemical vapor deposition of a dielectric silicon oxide film containing fluorine from an alkoxy-fluorosilane.